patch 8.0.1631: testing with Vim running in terminal is a bit flaky

Problem:    Testing with Vim running in terminal is a bit flaky.
Solution:   Delete any .swp file so that later tests don't fail.

src/testdir/screendump.vim

@@ -26,6 +26,10 @@ source shared.vim
"
" Options is a dictionary (not used yet).
func RunVimInTerminal(arguments, options)
  " If Vim doesn't exit a swap file remains, causing other tests to fail.
  " Remove it here.
  call delete(".swp")

  " Make a horizontal and vertical split, so that we can get exactly the right
  " size terminal window.  Works only when we currently have one window.
  call assert_equal(1, winnr('$'))

src/version.c

@@ -766,6 +766,8 @@ static char *(features[]) =

static int included_patches[] =
{   /* Add new patch number below this line */
/**/
    1631,
/**/
    1630,
/**/